<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    ul{
      border: 1px solid #e43;
    }
    div{
      margin-top: 10px;
      margin-bottom: 11px;
      background-color: aqua;
    }
  </style>
</head>
<body>
  <ul>
    <div id="a">11111</div>
    <div>ssfsfs</div>
     <button id="b"></button>
  </ul>
  <script>
    // 1 == parseInt(‘1M’) 
      var a = 10   ;
      var b =20 ;
      c=5;   
    console.log(++b+c+a++);
    console.log('bb==>',"1"+1 );
  </script>
</body>

</html>